In Japanese Patent Publication No. H10-203338, a brake-by-wire vehicle brake control device is proposed which has four pumps respectively for the four wheels of a vehicle. Two of the four pumps are located in a common conduit system for two of the four wheels and are driven by a common motor. The other two of the four pumps are located in another common conduit system for the other two of the four wheels and are driven by another common motor.
The inventor of the present invention gave consideration to the vehicle brake control device described above and found that pressure adjusting circuits can be installed respectively to the W/Cs and that linear valves can also be installed to the pressure adjusting circuits. In this case, differential pressures of the linear valves can be controlled by adjusting current values of currents to be supplied to the linear valves, in order to adjust the W/C pressures. Each of the differential pressures is a difference of pressure generated at the upstream side and the downstream side of a corresponding linear valve. Since the W/C pressures can be adjusted simply by controlling the current values for the linear valves, the W/C pressure changes in quick response to the amount of the operation of the brake pedal performed by a driver. More specifically, the W/C pressure can be controlled to change linearly depending on a pressure (hereinafter referred to as an M/C pressure) of a master cylinder (hereinafter referred to as an M/C) which changes in accordance with the amount of the operation of the brake pedal.
In this case, however, the W/C pressure changes so sensitively to the operation to the brake pedal that it changes even when the driver is not intentionally operating the brake pedal. This causes the driver to experience a bad brake feeling.